https验证证书的三个级别

一、无条件信任证书

1、

func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {

            if(challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust)

            {

                print(challenge.protectionSpace.host) 

                if(challenge.protectionSpace.host == "111.11.11.11")

                {

                    let credential = URLCredential(trust: challenge.protectionSpace.serverTrust!)

                   completionHandler(URLSession.AuthChallengeDisposition.useCredential, credential)

                }

            }

        }

2、

SecTrustSetAnchorCertificates(serverTrust, trustedCertList)

completionHandler(NSURLSessionAuthChallengePerformDefaultHandling,nil);

二、系统缺省验证：根据系统根证书验证证书链

completionHandler(NSURLSessionAuthChallengePerformDefaultHandling,nil);

三、证书强验证：根据本地保存的证书信息进行全面验证；

https://stackoverflow.com/questions/19507207/how-do-i-accept-a-self-signed-ssl-certificate-using-ios-7s-nsurlsession-and-its/20314162?r=SearchResults#20314162
https://www.jianshu.com/p/81eb390dc4c2